Fu­ture lies in net-zero

Small steps to­wards green build­ings will re­sult in a gi­ant leap to­wards sus­tain­able cities

Down to Earth - - LIFESTYLE - TANMAY TATHAGAT Prin­ci­pal at En­vi­ron­men­tal De­sign So­lu­tions, Delhi

THE IN­DIAN econ­omy has grown rapidly over the past decade and is ex­pected to sus­tain this growth over the next few decades. The coun­try’s build­ing sec­tor is growing in tan­dem with the econ­omy. In fact, the to­tal builtup area is ex­pected to swell five times of its cur­rent size by 2030. Pro­pelled by govern­ment poli­cies, such as “hous­ing for all” and “smart cities”, res­i­den­tial and com­mer­cial sec­tors will ex­pe­ri­ence max­i­mum growth. Such rapid growth will fur­ther in­crease our de­mand for en­ergy, wa­ter, min­er­als and other nat­u­ral re­sources, ex­ac­er­bat­ing en­vi­ron­men­tal prob­lems.

The build­ing con­struc­tion in­dus­try con­sumes 40 per cent of the ma­te­ri­als en­ter­ing the global econ­omy, and ac­counts for 40-50 per cent of the green­house gas ( ghg) emis­sions and agents of acid rain. Their im­pact on the environment would be even higher if one con­sid­ers the ghg emit­ted dur­ing the pro­duc­tion of ce­ment, bricks, steel, glass, alu­minium and other con­struc­tion ma­te­ri­als. Such con­cerns un­der­score the need to cre­ate sus­tain­able build­ings and cities world­wide.

But mak­ing build­ings truly sus­tain­able and green in In­dia re­mains a ma­jor chal­lenge. One of the ma­jor prob­lems is that our de­sign in­dus­try and de­vel­op­ers ape the Western de­sign and com­fort ideals, ig­nor­ing the fact that the cli­mate and life- style of Western coun­tries are dras­ti­cally dif­fer­ent from those of In­dia.

Be­sides, our pol­icy-mak­ing bod­ies at the Cen­tre are yet to un­der­stand the sig­nif­i­cance of en­ergy ef­fi­ciency in the build­ing sec­tor. Tough manda­tory stan­dards are wrongly seen as an im­ped­i­ment to growth and in­dus­try, and most poli­cies tend to opt for vol­un­tary com­pli­ances or less strin­gent stan­dards.

In the ab­sence of manda­tory stan­dards for green and en­ergy-ef­fi­cient build­ings, most mu­nic­i­pal­i­ties do not have a uni­form and prac­ti­cal en­ergy code, es­pe­cially for pas­sive and so­lar de­signs. Those who have the code in place do not have ef­fec­tive in­fra­struc­ture for its en­force­ment and ad­min­is­tra­tion. There are also no clear guide­lines for state and mu­nic­i­pal bod­ies for de­vel­op­ing and im­ple­ment­ing uni­form build­ing en­ergy ef­fi­ciency pro­grammes and poli­cies.

In­ter­na­tional ex­pe­ri­ence shows manda­tory and uni­formly im­ple­mented codes and stan­dards are the only way to achieve a sub­stan­tial im­pact of en­ergy-ef­fi­ciency mea­sure. Though the En­ergy Con­ser­va­tion Build­ing Code ( ecbc) is being im­ple­mented in In­dia, it is mod­er­ately strin­gent. The coun­try needs a dy­namic build­ing en­ergy pol­icy with long-term goals that can shape the fu­ture of the sec­tor.

A zero net-en­ergy build­ing tar­get could be a ma­jor leap in this di­rec­tion. This will spur in­no­va­tion for sus­tain­able and su­per-ef­fi­cient build­ings.

But be­fore set­ting the tar­get, the govern­ment must ad­dress the is­sues that de­ter peo­ple from adopt­ing green mea­sures, and must put in place a strat­egy to en­cour­age their mass ap­peal.

Con­sider this. In­dia has one of the high­est elec­tric­ity tar­iffs for com­mer­cial build­ings and the cost of en­ergy-ef­fi­cient tech­nolo­gies and re­new­able en­ergy sys­tems has re­duced over the years. Yet, their startup costs con­tinue to de­ter peo­ple from adopt­ing the prod­ucts and tech­nolo­gies. A big­ger mar­ket for them as well as a pol­icy environment pro­vid­ing sub­stan­tive in­cen­tives for de­vel­op­ment, im­ple­men­ta­tion and im­port of such prod­ucts and tech­nolo­gies are a must for high-per­for­mance build­ings to be main­streamed.

De­vel­op­ers tend to un­der-in­vest in green mea­sures be­cause they do not gain from the in­vest­ment made in en­ergy-ef­fi­cient build­ings, and thus pass on the cost of in­ef­fi­ciency to the buyer and the environment. The cur­rent high cost of bor­row­ing money can be a strong im­ped­i­ment to in­cre­men­tal fund­ing in ef­fi­ciency, which would be off­set by fu­ture sav­ings in en­ergy costs.

Fos­ter­ing an ethic for in­te­grated de­sign should be the most im­por­tant part of the strat­egy. A build­ing's en­ergy ef­fi­ciency, its abil­ity to gen­er­ate re­new­able en­ergy and its ar­chi­tec­tural de­sign and con­struc­tion can be in­te­grated to achieve the goal of sus­tain­abil­ity. But such in­te­gra­tion is not com­monly prac­tised. Many of the so­lu­tions for en­ergy ef­fi­ciency and green build­ings tend to be prod­uct-driven. Such prod­uct- and ven­dor-driven so­lu­tions could ad­dress in­di­vid­ual con­cerns in a project, but they do not pro­vide an in­te­grated and com­pre­hen­sive so­lu­tion. Most de­sign and con­struc­tion firms do not have in-house re­sources to do in­te­grated sus­tain­able de­sign. On the other hand, projects, which do in­vest in high per­for­mance build­ing de­sign, of­ten fail to get the de­sired re­sults be­cause of poor con­struc­tion, in­ad­e­quate com­mis­sion­ing and poor phys­i­cal in­te­gra­tion.

Ar­chi­tec­ture must also re­spond ap­pro­pri­ately to cli­mate and cul­ture. New com­mer­cial build­ings must be de­signed for day­light­ing and lim­it­ing so­lar heat gain. Res­i­den­tial build­ings must be sen­si­tive to the lo­cal cli­mate, and should have ap­pro­pri­ate ori­en­ta­tion for shad­ing, in­su­la­tion, sun protection and cool­ing through cross ven­ti­la­tion. Ad­dress­ing these con­cerns at the con­cept stage through pas­sive de­sign, such as day­light­ing, sun shades, evap­o­ra­tive cool­ing and nat­u­ral ven­ti­la­tion, only re­quires con­scious ef­forts and no in­cre­men­tal cost.

The ad­di­tional cost in­volved in mea­sures, such as in­su­la­tion, bet­ter glaz­ing and win­dow frames, usu­ally gets off­set by lower en­ergy use, with a pay­back pe­riod of less than five years.

Sim­u­la­tion for en­ergy per­for­mance of build­ings is a pow­er­ful tool that ar­chi­tects, en­gi­neers and de­vel­op­ers can use to an­a­lyse how the form, size, ori­en­ta­tion and type of build­ing af­fect the over­all en­ergy con­sump­tion of a build­ing. Of course, this anal­y­sis is ap­prox­i­mate and only as good as the in­puts pro­vided, but en­ergy mod­el­ling is a tool now ex­ten­sively used and pro­vides ac­cu­rate re­sults. For in­stance, glass plays an im­por­tant role in a build­ing’s over­all en­ergy con­sump­tion. But its ex­ces­sive use causes glare and over­heat­ing, while too lit­tle glaz­ing may re­duce day­light avail­able inside the build­ing. Ther­mal and light trans­mit­tance characteristics of glass vary from type to type, and build­ing sim­u­la­tion pro­grams can help strike a bal­ance be­tween day­light and heat gain to get the op­ti­mum

The cost of en­er­gy­ef­fi­cient tech­nolo­gies and re­new­able en­ergy sys­tems has re­duced over the years. Yet, their startup costs con­tinue to de­ter peo­ple from adopt­ing the prod­ucts and tech­nolo­gies

glass area re­quired, along with ther­mal and vis­ual spec­i­fi­ca­tions.

The skin of the build­ing—walls, win­dows and the roof—mod­er­ates the ef­fect of cli­mate. So, se­lec­tion of the build­ing en­ve­lope with ap­pro­pri­ate ther­mal mass, in­su­la­tion and colour can re­duce the num­ber of hours when heat­ing or cool­ing is re­quired to main­tain com­fort. Us­ing evap­o­ra­tive cool­ing through wa­ter­bod­ies and evap­o­ra­tive cool­ers can re­duce the re­quire­ment for air con­di­tion­ing (AC), es­pe­cially dur­ing the hot and dry pe­ri­ods. It is now pos­si­ble to seam­lessly in­te­grate evap­o­ra­tive cool­ing with con­ven­tional AC sys­tems. Ceil­ing fans have al­ways been a part of homes in In­dia, of­ten being the only source of com­fort in the sum­mer. They are now stag­ing a come back in com­mer­cial build­ings as well to en­hance ther­mal com­fort and to re­duce the en­ergy used in cool­ing.

To im­prove the qual­ity of life and environment in cities, many coun­tries are fo­cus­ing on re­duc­ing the en­vi­ron­men­tal im­pact of con­struc­tion to the min­i­mum pos­si­ble, mov­ing to­wards a goal of net­zero build­ings. In fact, tar­gets of net-zero en­ergy, wa­ter, or even carbon, have been set for many com­mu­ni­ties. Net-zero, or nearly-zero en­ergy build­ings ( nzebs), for ex­am­ple, have in­te­grated re­new­able en­ergy sys­tems that pro­duce as much en­ergy as the build­ing re­quires through­out the year. Such build­ings are likely to draw en­ergy dur­ing the peak pe­ri­ods from the grid, and give back ex­cess en­ergy pro­duced when their en­ergy de­mand is low. These build­ings har­ness all po­ten­tial ad­van­tages from the site, sur­round­ings and are de­signed for the cli­mate. The de­ci­sions about build­ing form, ori­en­ta­tion, shad­ing and ven­ti­la­tion, taken dur­ing the early de­sign stage have the most sig­nif­i­cant im­pact on the en­ergy con­sump­tion of the build­ing.

Pas­sive de­sign strate­gies help achieve ther­mal com­fort us­ing as lit­tle ac­tive cool­ing and heat­ing as pos­si­ble. This means re­duc­ing cool­ing re­quire­ment dur­ing the sum­mer and heat­ing in the win­ter through ap­pro­pri­ate ori­en­ta­tion, ex­ter­nal shad­ing, ap­pro­pri­ate amount of glaz­ing, and nat­u­ral ven­ti­la­tion. An nzeb will only be cost-ef­fec­tive if all the pas­sive strate­gies, all of which come at no-cost or low-cost, are in­cor­po­rated in its de­sign and con­struc­tion.

The next step is to es­tab­lish the in­door com­fort re­quire­ments based on adap­tive ther­mal com­fort stan­dards and to cal­cu­late the heat­ing and cool­ing loads through de­tailed hourly mod­el­ling. The ef­fect of air move­ment, ra­di­ant tem­per­a­tures, and dy­namic na­ture of build­ing op­er­a­tions dur­ing the day, as well as through the year, need to be con­sid­ered in de­sign­ing for com­fort lev­els. Per­form­ing hourly en­ergy sim­u­la­tion for the whole year will re­sult in the se­lec­tion of the most en­ergy-ef­fi­cient hvac (heat­ing, ven­ti­la­tion and air-con­di­tion­ing) de­sign. This de­tailed anal­y­sis be­comes es­sen­tial be­cause the worst con­di­tions oc­cur only for a few hours in a year, and the hvac loads re­main lower in the rest of the year. A well-de­signed sys­tem for an nzeb should be able to op­er­ate at these vari­able con­di­tions op­ti­mally.

Although there are sev­eral ex­cel­lent ex­am­ples of tra­di­tional build­ings that max­imise ther­mal and vis­ual com­fort in build­ings, these tra­di­tions need to be trans­formed, re­cal­i­brated and adapted for mod­ern de­sign of com­mer­cial build­ings.

The re­cent work in de­vel­op­ing an In­di­aspe­cific ther­mal com­fort stan­dard and cool­ing de­sign set-points spec­i­fied in the re­vised Na­tional Build­ing Code will al­low more ap­pro­pri­ate air­con­di­tion­ing sys­tem de­sign, but only if our de­sign sen­si­bil­i­ties and life­styles are in res­o­nance with the lo­cal cli­mate.

To im­prove the qual­ity of life and environment in cities, sev­eral coun­tries are set­ting tar­gets of net-zero en­ergy, wa­ter, or even carbon, for their com­mu­ni­ties

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